Anaplasmosis is an important tick-transmitted bacterial disease worldwide. The knowledge regarding transplacental transmission of anaplasmosis is lacking in Pakistan. The aim of the current study was to evaluate the prevalence, risk factors and to assess the transplacental transmission rate of A. marginale in pregnant dairy cows to their neonatal calves from the Sheikhupura and Chakwal districts of Punjab, Pakistan. A total of 796 blood samples were collected from pregnant cows and their neonatal calves (n=72). The pregnant cows were sampled at 60–90 days of gestation and subsequently just after parturition along with their neonatal calves for the detection of A. marginale before colostrum feeding using the msp1b gene-based PCR. The overall transplacental transmission rate in calves was 12.50%. District-wise transplacental transmission rate was 11.90% and 13.33% in Sheikhupura and Chakwal districts, respectively. Univariate logistic regression analysis indicated that season and area were significant risk factors (P<0.05; OR>1). However, multivariate logistic regression revealed that area was a significant risk factor. The sequencing and phylogenetic insights of representative isolates (OR854453 and OR738301) detected novel strains of A. marginale with 96–100% similarity with other countries. The msp1b gene-based phylogenetic tree uncovered that current isolates expressed homology with isolates from Pakistan, India, and Egypt. We can conclude that the intrauterine route of transmission should be considered while devising the prevention and control strategies for anaplasmosis as well as to prevent a significant number of neonatal mortalities.

To Cite This Article: Atif FA, Shujait MA, Haque SE and Khan I, 2025. Molecular surveillance and risk factors of Anaplasma marginale in pregnant cows in Pakistan with the evidence of transplacental transmission in neonatal calves. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.279